From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754632AbcIISnK (ORCPT ); Fri, 9 Sep 2016 14:43:10 -0400 Received: from mail-pa0-f54.google.com ([209.85.220.54]:35988 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754408AbcIISmd (ORCPT ); Fri, 9 Sep 2016 14:42:33 -0400 From: Omar Sandoval To: Jens Axboe , linux-block@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, Alexei Starovoitov Subject: [PATCH v3 5/5] sbitmap: randomize initial last_cache values Date: Fri, 9 Sep 2016 11:42:11 -0700 Message-Id: <38c544e501d976df00a7e13b3041fcfca2a117ed.1473446095.git.osandov@fb.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Omar Sandoval In order to get good cache behavior from a sbitmap, we want each CPU to stick to its own cacheline(s) as much as possible. This might happen naturally as the bitmap gets filled up and the last_cache values spread out, but we really want this behavior from the start. blk-mq apparently intended to do this, but the code to do this was never wired up. Get rid of the dead code and make it part of the sbitmap library. Signed-off-by: Omar Sandoval --- block/blk-mq-tag.c | 8 -------- block/blk-mq-tag.h | 1 - lib/sbitmap.c | 6 ++++++ 3 files changed, 6 insertions(+), 9 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index e1c2bed..cef618f 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -7,7 +7,6 @@ */ #include #include -#include #include #include "blk.h" @@ -419,13 +418,6 @@ void blk_mq_free_tags(struct blk_mq_tags *tags) kfree(tags); } -void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *tag) -{ - unsigned int depth = tags->nr_tags - tags->nr_reserved_tags; - - *tag = prandom_u32() % depth; -} - int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth) { tdepth -= tags->nr_reserved_tags; diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index f90b850..09f4cc0 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -30,7 +30,6 @@ extern void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx, unsigned int tag); extern bool blk_mq_has_free_tags(struct blk_mq_tags *tags); extern ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page); -extern void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *last_tag); extern int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int depth); extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool); void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 3a91269..d873bb0a 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -15,6 +15,7 @@ * along with this program. If not, see . */ +#include #include int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift, @@ -208,6 +209,11 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, return -ENOMEM; } + if (depth && !round_robin) { + for_each_possible_cpu(i) + *per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth; + } + sbq->wake_batch = SBQ_WAKE_BATCH; if (sbq->wake_batch > depth / SBQ_WAIT_QUEUES) sbq->wake_batch = max(1U, depth / SBQ_WAIT_QUEUES); -- 2.9.3